The present invention relates to a regulation for a gas engine with a rotational speed probe for the crankshaft rotational speed, with a memory of rotational speed-load-ignition angle performance graph (family of characteristic curves) read out during each crankshaft rotation with an ignition pulse generator controlled by the performance graph memory, with a lambda probe, with a load probe, with a vacuum controlled gas-pressure-adjusting device for the propulsion gas and with a gas-mixing device for the propulsion gas and air.
A gas engine offers a greater potential for the lean operation than a conventional Otto engine. This entails considerable advantages of the gas engine as regards fuel consumption and harmful component emission, especially in the partial load operation.
The mixture preparation with customary gas-mixing devices is disadvantageous as regards the flow resistance, the regulating ability and the failure susceptibility. It is also hardly possible with a control system to utilize the complete engine performance graph, especially if one desires to include the engine ignition. A control in particular does not assure optimum lambda values.
In "Bosch Technische Berichte"["Bosch Technical Reports"], 1981, No. 3, pages 139 to 151, reference is made to the use of an ignition performance graph (set of characteristic curves) and of a lambda performance graph (set of characteristic lambda curves) for the engine control. However, a control is possible in this manner only within a coarse raster.
The object of the present invention is the provision of a regulation for a gas engine which offers a complete utilization of the possibilities of the gas engine above all in the lean operation and in the partial load operation.
The underlying problems are solved according to the present invention in that a rotational speed-load-lambda-performance graph (set of characteristic curves) is provided for producing lambda-desired values, in that the lambda-desired values obtained from the rotational speed-load-lambda performance graph are compared with the lambda-existing values under formation of a lambda difference value, in that for the adaptation of the ignition angle to the respective lambda-actual value, a lambda-difference value-load-ignition angle correction performance graph produces an ignition angle correcting value which is added to the base ignition angle value of the rotational speed-load-ignition angle-performance graph, respectively, is subtracted therefrom.
The regulation of this invention differs from the state of the art insofar as a correction value on the basis of the measured lambda difference value is superimposed on the respective values of the base performance graphs for ignition angle and lambda value. As a result thereof, a regulation is superimposed on the control by the base performance graphs which compares the lambda-actual value with the lambda-desired value. The ignition angle is matched to the actual value of the engine and the mixture formation is corrected with a view toward the lambda-desired value. All characteristic values of the performance graphs, inclusive the correcting values, are stored as multi-bit terms or values in address locations of a memory unit so that they can be read out under the control of the input values (input signals) and can be combined in counters. These operations require no complicated and time-consuming calculation so that all adjusting values for the engine can be made available correctly in time during an operating period or cycle. The regulation also utilizes stored performance graphs (set of characteristic curves) of digital values.
A further feature of the present invention is characterized in that for the adaptation of the lambda value to different mixtures a rotational speed-load-lambda-correction performance graph is provided whose output values serve for the correction of the lambda-desired value.
One embodiment of the control of the gas pressure adjusting device provides that an adjusting valve is provided for the control of the vacuum for a diaphragm of the gas pressure adjusting device whereby the adjusting value is stored in a rotational speed-load-adjusting value-performance graph, and in that the diaphragm controls a valve body which releases the gas flow from a line into a gas line terminating in the venturi section of the gas-mixing device.
With the use of an adjusting valve controlled by current value, provision is made according to the present invention that the adjusting value is a current value for the adjusting valve.
A further embodiment of the gas pressure adjusting device of the present invention is characterized in that a gas valve flap is built into a line of the gas pressure adjusting device terminating in the gas-mixing device, whose adjusting value is stored in a rotational speed-load-adjusting value performance graph, and in that the diaphragm of the gas pressure adjusting device is acted upon with a constant vacuum and keeps open a valve body which controls the gas flow into the line.
With the use of a gas valve flap provision is made in the present invention that the adjusting value is an angle value for a gas valve flap.
A correction of the adjusting value thus leads to a regulating behavior that in addition to the rotational speed-load-adjusting value-performance graph, a lambda difference value-load-correcting value-performance graph is Provided whose correction values are added to the value of the base performance graph, respectively, are subtracted therefrom.
A further optimization is obtained by the present invention in that further correction performance graph as a function of the mixture pre-selection and of the acceleration conditions are provided whose correction values are added to the base values for ignition angle and gas-pressure adjusting device, respectively, are subtracted therefrom.
A control of the gas-mixing device also within the range of small through-flow becomes possible in that in addition to a main throttling device, a pre-throttling device is provided.
A particularly advantageous construction of the pre-throttling device is obtained in that the pre-throttling device is constructed as double-roller slide valve with adjustable cross-section which is effective in the lower through-flow range.